1. Field of the Invention
The present invention relates to novel viscoelastic viscosurgical materials and ophthalmic surgical techniques utilizing the materials.
2. Prior Art
In ophthalmic surgical procedures such as intraocular lens implantation, cataract surgery, retinal detachment repair, etc., there exists a need for viscous, gel-like compositions to fill the chambers of the eye to protect sensitive tissue such as the corneal endothelium from trauma. See U.S. Pat. No. 4,141,975; Pruett et al, Arch. Ophthalmol., 97:2325 (1979); Holmberg et al, Ophthalmology, 91:45 and 53 (1984); Pape et al, Ophthalmology, 87:669 (1980); MacRae et al, Am. J. Ophthalmol., 95:332 (1983); and Miller et al, Annals Ophthalmol., 13:811 (1981).
The most commonly employed materials are solutions of hyaluronic acid (HA), chondroitin sulfate (CS) and methylcellulose (MS). HA has been the most widely used and appears to owe its unusual rheological and viscoelastic solution properties to its polyanion polyelectrolyte molecular structure.
However, HA is extremely expensive. Furthermore, it requires extraordinary purification to remove as much proteinaceous immunogenic material as possible but still may provoke immune reactions in some patients. Its use is also often accompanied by significant undesirable intraocular pressure rise which necessitates washing HA from the eye at the end of surgery and may also require antiglaucoma therapy.
It has also been suggested to employ a solution of a relatively low molecular weight (i.e., 350,000) sodium carboxymethylcellulose as a "pseudovitreous fluid" in the posterior chamber [Wilhelmus et al, Annals of Ophthalmology, 16:350-352 (1984)]. In addition, Penkov et al [Oftalinol. Zh (USSR), 1984(4):215-217] discloses that 0.5% solutions of sodium carboxymethylcellulose may be used as a space filler in the eye.
It is an object of the present invention to provide improved ophthalmic viscoelastic surgical materials and ophthalmic surgical techniques embodying same which are not subject to the above-noted disadvantages.